This is an improvement of U.S. Pat. No. 4,842,405, where I am able to provide a tunable on-fiber Bragg gratings for telecommunication and other applications. The Bragg gratings are used in telecommunication links as a means for multiplexing, demultiplexing, coupling, or filtering optical signals at the Bragg wavelength. It is desirable to impart Bragg grating patterns on the surface of optical fibers. The methods available of producing Bragg gratings on the surface of optical fibers are essentially limited to producing the gratings on a flattened portion of the fiber and the grating thus produced covers only a small percent of the surface of the optical fiber core resulting in a polarization dependent structure. The only exception is the U.S. Pat. No. 4,842,405 which provides a method for constructing polarization independent Bragg gratings onto the entire cylindrical surface of the optical fiber, however, the Bragg gratings are not tunable.
It would be of great advantage for the art if tunable multiplexers, demultiplexers, couplers and filters could be built by forming tunable Bragg gratings on the entire cylindrical surface of the optical fiber core in a small section of the fiber is disclosed.
Another advantage would be to impose tunable gratings on the entire surface of the optical fiber as a polarization independent apparatus, the application of the device in telecommunication systems is vastly increased.
Other advantages will appear hereinafter.